Can the “space” option be set as variable?

GULP
1

Dear Developers and Users,

I am using USPEX2022.1 & GULP6.1.2 to predict the crystal structure of a small organic molecule. When finished, all space groups have reduced into P 1, though they were created in different space groups.

No such problem was met when other codes (for example, USPEX & VASP) were used.

I am confusing if there is something wrong with the “space” option in ginput file. According to the manual:

“The space option is not compulsory in the input of a structure and if it is absent then GULP will assume that the structure is in P 1 (i.e. no symmetry).”

My question: Can the “space” option be set as variable (which quote a number generated by USPEX) ?

If you can provide solutions, it will be a great help for a fresh user like me.

With best regards.

Wanlichuan

2

Dear Wanlichuan,
GULP will accept space group numbers (assuming the standard setting is being used) or the space group symbol (which allows for non-standard settings). So you can choose to either input the asymmetric unit and space group, or the full unit cell without symmetry - it’s up to you. The space group is never a variable in GULP (i.e. it stays the same as input by the user) as it’s not a continuous function that can be differentiated. You can use the phonons to check whether the space group choice is correct though by looking for imaginary modes in the Brillouin zone.
Best regards,
Julian

3

Dear julian,
I get it. Thanks a lot.

Wanlichuan